SEC-79 Add symbol table writer

src/util/symbol_table_writer.h

@@ -0,0 +1,163 @@
+
+// Copyright 2016-2017 DiffBlue Limited. All Rights Reserved.
+
+/// \file
+/// A symbol table writer that records which entries have been updated
+
+#ifndef CPROVER_UTIL_SYMBOL_TABLE_WRITER_H
+#define CPROVER_UTIL_SYMBOL_TABLE_WRITER_H
+
+#include <utility>
+#include <unordered_set>
+#include "irep.h"
+#include "symbol_table.h"
+
+/// \brief A symbol table wrapper that records which entries have been
+/// updated/removed
+/// \ingroup gr_symbol_table
+/// A caller can pass a `journalling_symbol_table_writert` into a callee that is
+/// expected to mutate it somehow, then after it has run inspect the recording
+/// table's journal to determine what has changed more cheaply than examining
+/// every symbol.
+///
+/// Example of usage:
+/// ```
+/// symbol_tablet real_table;
+/// init_table(real_table);
+///
+/// journalling_symbol_table_writert journal(actual_table); // Wraps real_table
+/// alter_table(journal);
+
+/// for(const auto &added : journal.added())
+/// {
+///   printf("%s was added\n", added.name);
+/// }
+class journalling_symbol_table_writert
+{
+public:
+  typedef std::unordered_set<irep_idt, irep_id_hash> changesett;
+private:
+  symbol_tablet &base_symbol_table;
+  // Symbols originally in the table will never be marked inserted
+  changesett inserted;
+  // get_writeable marks an existing symbol updated
+  // Inserted symbols are marked updated, removed ones aren't
+  changesett updated;
+  // Symbols not originally in the table will never be marked removed
+  changesett removed;
+
+private:
+  explicit journalling_symbol_table_writert(symbol_tablet &base_symbol_table):
+    base_symbol_table(base_symbol_table)
+  {
+  }
+
+public:
+  journalling_symbol_table_writert(
+    const journalling_symbol_table_writert &other):
+    base_symbol_table(other.base_symbol_table)
+  {
+  }
+
+  /// Permits implicit cast to const symbol_tablet &
+  operator const symbol_tablet &() const
+  {
+    return base_symbol_table;
+  }
+
+  static journalling_symbol_table_writert wrap(
+    symbol_tablet &base_symbol_table)
+  {
+    return journalling_symbol_table_writert(base_symbol_table);
+  }
+
+  bool add(const symbolt &symbol)
+  {
+    bool ret=base_symbol_table.add(symbol);
+    if(!ret)
+      on_insert(symbol.name);
+    return ret;
+  }
+
+  bool move(symbolt &symbol, symbolt *&new_symbol)
+  {
+    bool ret=base_symbol_table.move(symbol, new_symbol);
+    if(!ret)
+      on_insert(symbol.name);
+    else
+      on_update(symbol.name);
+    return ret;
+  }
+
+  symbolt *get_writeable(const irep_idt &identifier)
+  {
+    symbolt *result=base_symbol_table.get_writeable(identifier);
+    if(result)
+      on_update(identifier);
+    return result;
+  }
+
+  symbolt &get_writeable_ref(const irep_idt &identifier)
+  {
+    // Run on_update *after* the get-ref operation in case it throws
+    symbolt &result=base_symbol_table.get_writeable_ref(identifier);
+    on_update(identifier);
+    return result;
+  }
+
+  std::pair<symbolt &, bool> insert(symbolt symbol)
+  {
+    std::pair<symbolt &, bool> result=
+      base_symbol_table.insert(std::move(symbol));
+    if(result.second)
+      on_insert(result.first.name);
+    return result;
+  }
+
+  bool remove(const irep_idt &id)
+  {
+    bool ret=base_symbol_table.remove(id);
+    if(!ret)
+      on_remove(id);
+    return ret;
+  }
+
+  void erase(const symbol_tablet::symbolst::const_iterator &entry)
+  {
+    base_symbol_table.erase(entry);
+    on_remove(entry->first);
+  }
+
+  void clear()
+  {
+    for(const auto &named_symbol : base_symbol_table.symbols)
+      on_remove(named_symbol.first);
+    base_symbol_table.clear();
+  }
+
+  const changesett &get_inserted() const { return inserted; }
+  const changesett &get_updated() const { return updated; }
+  const changesett &get_removed() const { return removed; }
+
+private:
+  void on_insert(const irep_idt &id)
+  {
+    if(removed.erase(id)==0)
+      inserted.insert(id);
+    updated.insert(id);
+  }
+
+  void on_update(const irep_idt &id)
+  {
+    updated.insert(id);
+  }
+
+  void on_remove(const irep_idt &id)
+  {
+    if(inserted.erase(id)==0)
+      removed.insert(id);
+    updated.erase(id);
+  }
+};
+
+#endif // CPROVER_UTIL_SYMBOL_TABLE_WRITER_H

unit/Makefile

@@ -31,6 +31,7 @@ SRC += unit_tests.cpp \
        util/expr_iterator.cpp \
        util/message.cpp \
        util/simplify_expr.cpp \
+       util/symbol_table.cpp \
        catch_example.cpp \
        # Empty last line